Project Summary Lung cancer is a devastating disease that remains the top cause of cancer mortality. Despite recent advances, the majority of patients with lung cancer lack effective therapeutic options, underscoring the dire need for additional treatment approaches. Genomic studies have identified frequent mutations in subunits of the SWI/SNF chromatin remodeling complex including SMARCA4 and ARID1A in non-small cell lung cancer with a frequency of up to 33% in advanced stage disease, making it the most frequently mutated complex in lung cancer. We recently demonstrated that Smarca4 acts as a bona fide tumor suppressor in mice and cooperates with p53 loss and Kras activation. Importantly, SMARCA4 mutant cancer cells have heightened sensitivity to inhibition of oxidative phosphorylation (OXPHOS) by a novel small molecule, IACS-10759. Mechanistically, we showed that SMARCA4-deficient cells have a blunted transcriptional response to energy stress creating a therapeutically relevant vulnerability. Taking these observations together, we hypothesize that OXPHOS inhibition using IACS-10759 is an attractive therapeutic strategy for lung cancers with mutations in the SWI/SNF complex. The major objectives of the proposed study are to discover the mechanistic basis of the metabolic rewiring in SWI/SNF mutants and provide preclinical evidence to guide future clinical study of IACS-10759 in patients with SWI/SNF mutant lung cancer. Due to the unique microenvironment of lung cancer including high local oxygen tension, it is imperative to study therapeutic agents targeting metabolism orthotopically. Hence, we will test efficacy of IACS-10759 in GEM models of lung cancer. Further, PDX models have emerged as powerful tools to help guide treatment strategies. Thus, we propose to determine the potential of OXPHOS inhibition in various SWI/SNF mutant PDX model systems. While our preliminary data indicates that IACS-10759 treatment leads to tumor growth inhibition, synergistic combination strategies are expected to be even superior in efficacy. Thus, we propose to identify optimal combination agents that synergize with IACS-10759 by using a chemo-genetic screen. Here, we will use CRISPR-Cas9 and a custom designed library of guide RNAs against genes targeted by FDA approved drugs (FDAome). We will validate the results of the screen by performing one-on-one drug combination studies in vivo. Finally, our preliminary data suggests that SMARCA2 is required for expression of PGC1?, a master transcriptional regulator of mitochondrial biogenesis and OXPHOS, in SMARCA4 mutant cells. We know from our published work that PGC1? is essential in SMARCA4 deficient cells. Thus we hypothesize that SMARCA2 is a survival factor and a major driver of metabolic rewiring in SMARCA4 deficient cells in a PGC1? dependent manner. In conclusion, our study is expected to provide mechanistic insight into the metabolic dysregulation of SWI/SNF mutant lung cancers and lay the foundation for future clinical development of the OXPHOS inhibitors as therapeutics.